Rotary fuel pump

Some types of the Mitsubishi S4S engines uses rotary injection diesel pumps. These types of pumps have only one fuel-metering plunger.
A spinning rotor makes the connection with the different fuel distribution pipes on the distributor head.
The benefits of a rotary-fuel injection pump with only one plunger is: all the shots of diesel are exactly the same. Also, rotary fuel pumps have less moving parts compared to inline fuel pumps.